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An absorber with lightweight, low-cost, high absorption and broad frequency bandwidth is highly expected to design an electromagnetic wave absorber application. In this paper, the carbon materials based agricultural waste from oil palm empty fruit bunch (OPEFB) were studied to investigate the electromagnetic wave, especially the microwave absorption properties within the range from 8 to 12 GHz (X-band). The carbon-based OPEFB is prepared by hydrothermal carbonization (at 180 oC for 8 hours) followed by chemical (using KOH activating agent) and physical (at 800 oC for 2 hours) of carbonization processes. We studied the microwave absorption properties of the porous carbon-based OPEFB with 20 % of KOH concentration. A vector network analyzer (VNA) takes the microwave absorption properties within the X-band frequency range. The results indicate the ability to absorb electromagnetic waves in all X-band frequencies for porous activated carbon-based OPEFB samples. The reflection loss is reach -32.21 dB at 10.64 GHz. The enhancement of EM wave absorption in activated carbon-based OPEFB compared to that of raw OPEFB material is correlated to the formation of porous stracture inducing the multiple reflection to enhance the interfacial polarization of EM wave. This research show that the porous carbon-based OPEFB can be a promising candidate for a lightweight, green, and renewable of electromagnetic waves absorber in the future. [ABSTRACT FROM AUTHOR]

Zinc oxide nanorods/Graphene (ZnO NRs/Gr) were synthesized using an easy and fast method; spray for ZnO seed and graphene deposition and hydrothermal for ZnO NRs. The sample was varied by using different ZnO seed precursor of 0.1 M, 0.2 M, and 0.3 M. We found that the greater the concentration of ZnO led to a decrease in porosity, accompanied by an increase in the water contact angle of 150°, 153°, and 155°. The XRD results confirmed that there was no shift in the ZnO peak, which indicated that there was no significant structural change due to the lattice strain. UV-Vis analysis obtained a band gap of ∼3.4 eV and an excited state of ∼4 eV. Based on the results obtained, ZnO NRs/Graphene can be a promising waterproof coating material on cotton fabrics. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) has a broad range of applications such as wastewater treatment, gas separation, purification, energy storage, and adsorbents. However, the majority of commercially activated carbons are made from nonrenewable fossil-based material. Therefore, biomass-derived activated carbon has attracted much attention in replacing fossil-based carbon precursors due to environmental issues. In this research, Oil palm shell (OPS), as one of local commodity by-products in Indonesian oil palm industry, was used as a raw material due to its high lignin content to produce high-yield AC to investigate the effect of different activator agents on the adsorption capability of materials. By varying the activator agents which are H3PO4 and ZnCl2, hydrothermal and pyrolysis method were conducted at 220°C for 8 hours and at 800°C for 1 hour, respectively. Raman spectroscopy, X-Ray Diffraction, and N2 Adsorption-Desorption measurements were used to characterize the structural properties of our ACs. The moisture content, ash content, volatile matter, and fixed carbon of the samples were tested and have met SNI standard 06-3730-1995 for technical activated carbon. The structural results indicate that our material has an amorphous structure with the dominance of microstructure pores while the highest surface area is owned by AC with an H3PO4 activator with a value of 859.52 m2/g. The adsorption capability of AC was tested through Methylene Blue and Rhodamine B adsorption which indicate that our materials have approached SNI standard and show good capability of adsoprtion. In general, this material can potentially be used for adsorbents to purify liquids in many applications especially to reduce color in wastewater treatments. [ABSTRACT FROM AUTHOR]

Natural fibers are abundant in Indonesia, coconut fiber (Cocos nucifera) is used as an insulation composite for wall fillers. In general non-natural materials such as glass wool, polyurethane, fiberglass, polyimide foam, and other synthetic materials are still used as substitutes for insulation, which has been using synthetic materials since the use of coconut fiber as agricultural waste. This research is to analyze the quality of the fiberboard's physical and mechanical properties. To know quality product physical and mechanical tests such as density, moisture content, water absorption, thickness expansion, compression, and bending (standardized using JIS A 5905 2003) and morphological analysis were carried out to determine visual characterization using a 3D keyence microscope on a fiberboard. Making a test sample with a size of 210 x 120 x 5 cm, coconut fiber is mixed with polyurethane adhesive with a density variation of 0.04, 0.06, 0,08, and 0.1, then cold-pressed at a pressure of 5 kg/cm2 for 2 hours because the polyurethane adhesive is thermosetting, and then cut to a size of 30 x 30 cm. The results showed that the higher the density of the fiberboard, the better the physical and mechanical properties. A density of 0.1 g/cm3 produces the best mechanical properties. [ABSTRACT FROM AUTHOR]

Activated carbon is an amorphous material that is widely used as a filter, adsorbent, electrode material, etc. However, conventional activated carbon is non-eco-friendly material due to its unsustainable issue, therefore, biomass-based activated carbon (AC) has become popular research in order to replace fossil-based activated carbon. In this study, we used oil palm waste as our raw materials from different parts of the oil palm tree such as Oil Palm Empty Fruit Bunches (OPEFB), and Oil Palm Shells (OPS). The different structures of activated carbon from oil palm waste will be investigated through OPEFB and OPS while the differences in carbonization methods between hydrothermal and pyrolysis were performed on OPS and OPS-char. These materials were activated using solid KOH and FeCl2.H2O, followed by pyrolysis at 800oC in an N2 atmosphere. Physical characterization was carried out by proximate analysis to determine the quality of activated carbon using ASTM standards. Meanwhile, the structural characterization was carried out using XRD, BET, and FESEM methods to observe the structural morphology of each activated carbon. The proximate analysis results show good results that meet ASTM standards D 3172-3175 with low moisture, ash content, volatile matter, and high fixed carbon values. The highest value in the methylene blue adsorption test was found in AC OPEFB. XRD analysis showed that our samples have an amorphous structure while BET analysis presents our samples have high surface area namely, AC OPEFB (775.58 m2/g), AC OPS (733.04 m2/g), and AC OPS-char (594.093 m2/g). The FESEM images show the formed AC pores depending on the natural structure and type of carbonization method. In general, these material properties can be applied to pore-based applications such as adsorbents in wastewater treatment or electrodes in energy storage. [ABSTRACT FROM AUTHOR]

Hydrophilic cotton fabric (WCA = 68°) was successfully converted to superhydrophobic (WCA > 150°) by coating the surface with ZnO nanoparticles (NPs) using the hydrothermal method without additional reagent. We noted that the ZnO particle size, as well as the sample surface density, increased with the higher precursor concentrations, forming hierarchical morphology. Interestingly, the coexistence of the excitonic state (∼ 4 eV) and the defect state (2 - 3.2 eV) was observed, which has the potential for developing a water-repellent and anti-bacterial surface. The role of morphology on absorption and wettability properties is then studied comprehensively. Our results can be used as a strategy for designing water-repellent and anti-bacterial coatings for medical and textile applications. [ABSTRACT FROM AUTHOR]

The development of particleboard made from non-wood lignocellulose materials and natural adhesives has become intensive research due to the lack of wood supply and fossil resources. In this study, coconut husk and citric acid were used as the raw material and natural adhesive for new generation of particleboards. The effect of particles size and citric acid content in the physical properties of the particleboards were investigated. The particles sizes of coconut husk were divided into 3 sizes of mesh such as 4, 10, and 14 while citric acid content was varied in the range of 15 to 25 wt%. Thermo-pressing technique was conducted in 200 °C for 10 min. 300 mm x 300 mm x 9 mm board size was formed for 0.8 g/cm3 target density. The physical properties of particleboards are improved from smaller to bigger particle size (4 to 14 mesh) proportional to the increment of citric acid content until 20 wt%. Type 18 JIS A 5908 (2003) standard was satisfied in physical properties of particleboards for 14 mesh of particles and 25 wt% citric acid binder. Consequently, it was concluded that 14 mesh of the particles size and a citric acid content of 25 wt% were effective in manufacturing particleboards composed of coconut husk and citric acid. [ABSTRACT FROM AUTHOR]

We have investigated optical properties of Ta-doped TiO2 thin film on LaAlO3 (LAO) substrate using Spectroscopic Ellipsometry (SE) at room temperature. Amplitude ratio Ψ and phase difference Δ between p- and spolarized light waves are obtained by multiple incident angles measurement (60°, 70°, and 80°) at energy range of 0.5 - 6.5 eV. In order to obtain optical properties for every Ta concentrations (0.01, 0.4, and 5 at. %), multilayer modelling was performed simultaneously by using Drude-Lorentz model. Refractive index and optical dispersion parameters were determined by Wemple-DiDomenico relation. In general, refractive index at zero photon energy n(0) increases by increasing Ta concentration. Furthermore, optical band gap shows a significant increasing due to presence of Ta dopant. In addition, other optical constants are discussed as well. [ABSTRACT FROM AUTHOR]